Peripheral nitric oxide in carrageenan-induced inflammation

In vivo and in vitro anti-inflammatory activity of neorogioltriol, a new diterpene extracted from the red algae Laurencia glandulifera

Neorogioltriol is a tricyclic brominated diterpenoid isolated from the organic extract of the red algae Laurencia glandulifera. In the present study, the anti-inflammatory effects of neorogioltriol were evaluated both in vivo using carrageenan-induced paw edema and in vitro on lipopolysaccharide (LPS)-treated Raw264.7 macrophages. The in vivo study demonstrated that the administration of 1 mg/kg of neorogioltriol resulted in the significant reduction of carregeenan-induced rat edema. In vitro, our results show that neorogioltriol treatment decreased the luciferase activity in LPS-stimulated Raw264.7 cells, stably transfected with the NF-κB-dependent luciferase reporter. This effect on NF-κB activation is not mediated through MAPK pathways. The inhibition of NF-κB activity correlates with decreased levels of LPS-induced tumor necrosis factor-alpha (TNFα) present in neorogioltriol treated supernatant cell culture. Further analyses indicated that this product also significantly inhibited the release of nitric oxide and the expression of cyclooxygenase-2 (COX-2) in LPS-stimulated Raw264.7 cells. These latter effects could only be observed for neorogioltriol concentrations below 62.5 μM. To our knowledge, this is the first report describing a molecule derived from Laurencia glandulifera with anti-inflammatory activity both in vivo and in vitro. The effect demonstrated in vitro may be explained by the inhibition of the LPS-induced NF-κB activation and TNFα production. NO release and COX-2 expression may reinforce this effect.

Anti-inflammatory properties of doxycycline and minocycline in experimental models: an in vivo and in vitro comparative study

AIMS AND METHODS

Minocycline (Mino) and doxycycline (Dox) are second generation tetracyclines known to present several other effects, which are independent from their antimicrobial activities. We studied in a comparative way the anti-inflammatory effects of Mino and Dox, on acute models of peripheral inflammation in rodents (formalin test and peritonitis in mice, and carrageenan-induced paw oedema in rats). Immunohistochemical assays for TNF-alpha and iNOS in rat paws of carrageenan-induced oedema were also carried out as well as in vitro assays for myeloperoxidase (MPO) and lactate dehydrogenase (LDH). Furthermore, antioxidant activities were evaluated by the DPPH assay.

RESULTS

In the formalin test although Mino and Dox (1, 5, 10 and 25 mg/kg, i.p.) inhibited the first phase, they acted predominantly on the second phase of the test, where inhibition of the licking time close to 80% were observed. Mino and Dox were very efficacious in reducing the carrageenan-induced paw oedema in rats (10, 25 and 50 mg/kg, i.p.) and carrageenan-induced leucocyte migration (1 and 5 mg/kg, i.p.) to mice peritoneal cavities. Besides, they also significantly inhibited MPO and LDH releases at doses ranging from 0.001 to 1 μg/ml. Thus, in general, the anti-inflammatory activity of Dox was higher as compared to that of Mino, although the radical scavenging activity of Mino was of a magnitude 10 times higher.

CONCLUSIONS

Our data indicate that anti-inflammatory and antioxidant effects, involve the inhibition of iNOS and TNF-alpha, among other properties, and these encourage clinical studies of these compounds for new therapeutic applications, especially those were inflammation plays a role.

Effect of acute topical application of +-pentazocine on the mechanical allodynia in diabetic mice

Mechanical allodynia is a major complication in diabetic mellitus. Peripheral sigma(1) receptors were shown to be involved in nociceptive perception. We therefore investigated the effect of sigma(1) receptor ligand (+)-pentazocine injected into the dorsal surface of the hindpaw on mechanical allodynia in streptozotocin-induced diabetic mice. Injection of (+)-pentazocine (30 microg) into the dorsal surface of the hindpaw did not affect the mechanical threshold and hindpaw NO contents in non-diabetic mice, whereas the mechanical allodynia and hindpaw contents of NO metabolites in diabetic mice were normalized by (+)-pentazocine. These effects of (+)-pentazocine in diabetic mice were inhibited by pretreatment with an sigma receptor antagonist BD1047 into the same area, but not by systemic pretreatment with a kappa-opioid receptor antagonist nor-binaltorphimine. These results suggest that (+)-pentazocine injected into the dorsal surface of the hindpaw increases the lowered mechanical threshold in diabetic mice through the activation of peripheral sigma(1) receptors. This attenuation may be, in part, due to the normalization of increased peripheral NO contents in the hindpaw of diabetic mice.

Reactive nitroxidative species and nociceptive processing: determining the roles for nitric oxide, superoxide, and peroxynitrite in pain

Pain is a multidimensional perception and is modified at distinct regions of the neuroaxis. During enhanced pain, neuroplastic changes occur in the spinal and supraspinal nociceptive modulating centers and may result in a hypersensitive state termed central sensitization, which is thought to contribute to chronic pain states. Central sensitization culminates in hyperexcitability of dorsal horn nociceptive neurons resulting in increased nociceptive transmission and pain perception. This state is associated with enhanced nociceptive signaling, spinal glutamate-mediated N-methyl-D: -aspartate receptor activation, neuroimmune activation, nitroxidative stress, and supraspinal descending facilitation. The nitroxidative species considered for their role in nociception and central sensitization include nitric oxide (NO), superoxide ([Formula: see text]), and peroxynitrite (ONOO(-)). Nitroxidative species are implicated during persistent but not normal nociceptive processing. This review examines the role of nitroxidative species in pain through a discussion of their contributions to central sensitization and the underlying mechanisms. Future directions for nitroxidative pain research are also addressed. As more selective pharmacologic agents are developed to target nitroxidative species, the exact role of nitroxidative species in pain states will be better characterized and should offer promising alternatives to available pain management options.

Caffeic Acid Derivatives: In Vitro and In Vivo Anti-inflammatory Properties

Caffeic acid and some of its derivatives such as caffeic acid phenetyl ester (CAPE) and octyl caffeate are potent antioxidants which present important anti-inflammatory actions. The present study assessed the in vitro and in vivo effects of five caffeic acid derivatives (caffeic acid methyl, ethyl, butyl, octyl and benzyl esters) and compared their actions to those of CAPE. In the model of LPS-induced nitric oxide (NO) production in RAW 264.7 macrophages, the pre-incubation of all derivatives inhibited nitrite accumulation on the supernatant of stimulated cells, with mean IC50 (microM) values of 21.0, 12.0, 8.4, 2.4, 10.7 and 4.80 for methyl, ethyl, butyl, octyl, benzyl and CAPE, respectively. The effects of caffeic acid derivatives seem to be related to the scavenging of NO, as the compounds prevented SNAP-derived nitrite accumulation and decreased iNOS expression. In addition, butyl, octyl and CAPE derivatives significantly inhibited LPS-induced iNOS expression in RAW 264.7 macrophages. Extending the in vitro results, we showed that the pre-treatment of mice with butyl, octyl and CAPE derivatives inhibited carrageenan-induced paw edema and prevented the increase in IL-1beta levels in the mouse paw by 30, 24 and 36%, respectively. Butyl, octyl and CAPE derivatives also prevented carrageenan-induced neutrophil influx in the mouse paw by 28, 49 and 31%, respectively. Present results confirm and extend literature data, showing that caffeic acid derivatives exert in vitro and in vivo anti-inflammatory actions, being their actions mediated, at least in part by the scavenging of NO and their ability to modulate iNOS expression and probably that of other inflammatory mediators.

Pre-emptive anti-hyperalgesic effect of electroacupuncture in carrageenan-induced inflammation: role of nitric oxide

Central sensitization theory has been defined as pivotal for understanding the excitability changes in central neurons following peripheral inflammation or neuropathic injury. Considerable evidence has demonstrated that activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors and subsequent nitric oxide (NO) production are the key in these changes. Consequently, neuromodulator drugs have been developed during the last decades. The electroacupuncture (EA) that acts as biochemical modulator in the spinal horn cord would prevent these changes. The aim of this study was to determine the thermal anti-hyperalgesic effect of EA (10 Hz, 3 mA) and its combination with L-NAME as nitric oxide synthase (NOS) inhibitor in carrageenan-induced hyperalgesia in rats. Also, it investigated the changes in the plasmatic concentrations of NO metabolites. Moreover, the EA combination with sub-effective dose of ketamine as a NMDA antagonist was tested. The EA pre-treatment conducted in unsedated, unrestrained and conscious animals showed a thermal anti-hyperalgesic effect in correspondence with plasmatic increase of NO metabolites. The L-NAME (30 mg/kg) pre-administration decreased significantly the plasmatic concentrations of NO(2)(-)/NO(3)(-) and suppressed the anti-hyperalgesic effect of EA. The combination of EA with ketamine enhanced the anti-hyperalgesic effect. These data constitute the first report that suggested the participation, at least in part, of the L-arginine-NOS-NO-GMPc pathway activation in anti-hyperalgesic effect of EA in carrageenan-induced inflammation model.

Anti-inflammatory effects of sinapic acid through the suppression of inducible nitric oxide synthase, cyclooxygase-2, and proinflammatory cytokines expressions via nuclear factor-kappaB inactivation

To investigate the anti-inflammatory potential of sinapic acid as well as the underlying mechanism involved, we studied the inhibitory effect of sinapic acid on the production of pro-inflammatory mediators in vitro and then evaluated its in vivo anti-inflammatory effect. Sinapic acid inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO), prostaglandin E 2 (PGE 2), tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1beta production in a dose-dependent manner. Consistent with these findings, sinapic acid inhibited LPS-induced expressions of inducible nitric oxide synthase (iNOS) and cyclooxygase (COX)-2 at the protein levels, and iNOS, COX-2, TNF-alpha, and IL-1beta mRNA expression in RAW 264.7 macrophages, as determined by Western blotting and reverse-transcribed polymerase chain reaction, respectively. Sinapic acid suppressed the LPS-induced activation of nuclear factor-kappaB (NF-kappaB), a transcription factor pivotal necessary for pro-inflammatory mediators, such as iNOS, COX-2, TNF-alpha, and IL-1beta. This effect was accompanied by a parallel reduction of the nuclear translocation of p65 and p50 NF-kappaB subunits, as well as IkappaB-alpha degradation and phosphorylation. The effects of sinapic acid on acute phase inflammation were investigated on serotonin- and carrageenan-induced paw edema and compared with indomethacin (10 mg/kg, p.o.) or ibuprofen (100 mg/kg, p.o.). Maximum inhibitions of 34.2 and 44.5% were observed at a concentration of 30 mg/kg for serotonin- and carrageenan-induced paw edema, respectively. These results suggest that the suppressions of the expressions of iNOS, COX-2, TNF-alpha, and IL-1beta via NF-kappaB inactivation are responsible for the anti-inflammatory effects of sinapic acid.

Anti-inflammatory effects of liquiritigenin as a consequence of the inhibition of NF-kappaB-dependent iNOS and proinflammatory cytokines production

BACKGROUND AND PURPOSE

Glycyrrhizae radix has been widely used as a cytoprotective, plant-derived medicine. We have identified a flavanoid, liquiritigenin, as an active component in extracts of Glycyrrhizae radix. This research investigated the effects of liquiritigenin on the induction of inducible NOS (iNOS) and proinflammatory cytokines by lipopolysaccharide (LPS) in Raw264.7 cells, and on paw oedema in rats.

EXPERIMENTAL APPROACH

iNOS expression was determined by western blotting, real-time reverse transcription-PCR and reporter gene analyses. Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta and IL-6 were assayed by ELISA. Gel shift assay and immunoblotting were used to assess NF-kappaB activation. The effect of liquiritigenin on acute inflammation in vivo was evaluated using carrageenan-induced paw oedema.

KEY RESULTS

Treatment of Raw264.7 cells with liquiritigenin caused inhibition of LPS-induced NF-kappaB DNA binding activity, due to repression of I-kappaBalpha phosphorylation and degradation. Liquiritigenin treatment prevented LPS from increasing the levels of iNOS protein and mRNA in a concentration-dependent manner. Liquiritigenin also suppressed the production of TNF-alpha, IL-1beta and IL-6 from Raw264.7 cells after LPS. In rats, liquiritigenin treatment inhibited formation of paw oedema induced by carrageenan.

CONCLUSION AND IMPLICATIONS

These results demonstrate that liquiritigenin exerts anti-inflammatory effects, which results from the inhibition of NF-kappaB activation in macrophages, thereby decreasing production of iNOS and proinflammatory cytokines. Our findings showing inhibition by liquiritigenin of paw oedema as well as inflammatory gene induction will help to understand the pharmacology and mode of action of liquiritigenin, and of the anti-inflammatory use of Glycyrrhizae radix.

Anti-inflammatory activity of 21(α, β)-methylmelianodiols, novel compounds from Poncirus trifoliata Rafinesque

The fruits of Poncirus trifoliata (L.) are widely used in Oriental medicine as a remedy for allergic inflammation. As a part of our program to screen medicinal plants for potential anti-inflammatory compounds, 21alpha-methylmelianodiol (21alpha-MMD) and 21beta-methylmelianodiol (21beta-MMD), which are two isomers of 21-methylmelianodiol isolated from the fruits of P. trifoliata for the first time, were found to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. 21alpha-MMD and 21beta-MMD attenuated LPS-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 protein expressions as well as the mRNA levels of iNOS, COX-2, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta). To investigate the mechanism involved, we examined the effect of 21alpha-MMD and 21beta-MMD on LPS-induced nuclear factor-kappaB (NF-kappaB) activation. Both 21alpha-MMD and 21beta-MMD significantly inhibited LPS-induced NF-kappaB transcriptional activity in RAW 264.7 macrophages. Moreover, the in vivo anti-inflammatory effect of 21alpha-MMD was examined in two mouse models of acute inflammation. In the carrageenan-induced paw edema model, administration of 21alpha-MMD (20 and 100 mg/kg, i.p.) dose-dependently reduced paw swelling. In addition, 21alpha-MMD significantly inhibited the dye leakage in an acetic acid-induced vascular permeability assay. Taken together, our data indicate that 21-methylmelianodiol is an important constituent of the fruit of P. trifoliata, and that the inhibition of iNOS and COX-2 expression by 21alpha-MMD and 21beta-MMD might be one of the mechanisms responsible for their anti-inflammatory effects.

Inducible nitric oxide synthase and cyclooxygenase-2 participate in anti-inflammatory and analgesic effects of the natural marine compound lemnalol from Formosan soft coral Lemnalia cervicorni

Lemnalol (8-isopropyl-5-methyl-4-methylene-decahydro-1,5-cyclo-naphthalen-3-ol) is a natural compound isolated from the marine soft coral Lemnalia cervicorni. In the present study, the anti-inflammatory and anti-nociceptive properties of lemnalol were investigated in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and carrageenan-injected rats, respectively. Our results demonstrate that lemnalol significantly inhibited the expression of the pro-inflammatory proteins, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), in LPS-stimulated RAW 264.7 cells. An in vivo inflammation model was induced by intraplantar injection of carrageenan into rat hind paws. An intramuscular injection of lemnalol (15 mg/kg) 10 min before carrageenan injection resulted in significant inhibition of carrageenan-induced rat paw edema and thermal hyperalgesia behavior. Western blot experiments revealed that the carrageenan-induced expression of iNOS and COX-2 in paw tissue was significantly down-regulated by lemnalol. Moreover, post-intrathecal injection of lemnalol produced a dose-dependent anti-nociceptive effect in carrageenan-injected rats (1 and 5 microg). The present results indicate that the marine-derived compound lemnalol had anti-inflammatory and analgesic effects in LPS-stimulated RAW 264.7 cells and carrageenan-injected rats, respectively. In addition, inhibition of elevated iNOS and COX-2 protein expression as well as neurophil infiltration of carrageenan-injected paws may be involved in the beneficial effects of lemnalol.

Neurobiology of pain

The neurobiology of pain had a notable interest in research focused on the study of neuronal plasticity development, nociceptors, molecular identity, signaling mechanism, ionic channels involved in the generation, modulation and propagation of action potential in all type of excitable cells. All the findings open the possibility for developing new therapeutic treatment. Nociceptive/inflammatory pain and neuropathic pain represent two different kinds of persistent chronic pain. We have reviewed the different mechanism suggested for the maintenance of pain, like descending nociceptive mechanism and their changes after tissue damage, including suppression and facilitation of defence behavior during pain. The role of these changes in inducing NMDA and AMPA receptors gene expression, after prolonged inflammation is emphasized by several authors. Furthermore, a relation between a persistent pain and amygdale has been shown. Molecular biology is the new frontier in the study of neurobiology of pain. Since the entire genome has been studied, we will able to find new genes involved in specific condition such as pain, because an altered gene expression can regulate neuronal activity after inflammation or tissue damage.

(−)-Linalool inhibits in vitro NO formation: Probable involvement in the antinociceptive activity of this monoterpene compound

Recent studies performed in our laboratory have shown that (-)-linalool, the natural occurring enantiomer in essential oils, possesses anti-inflammatory, antihyperalgesic and antinociceptive effects in different animal models. The antinociceptive and antihyperalgesic effect of (-)-linalool has been ascribed to the stimulation of the cholinergic, opioidergic and dopaminergic systems, to its local anaesthetic activity and to the blockade of N-Methyl-d-aspartate receptors (NMDA). Since nitric oxide (NO) and prostaglandin E(2) (PGE(2)) play an important role in oedema formation and hyperalgesia and nociception development, to investigate the mechanism of these actions of the (-)-linalool, we examined the effects of this compound on lipopolysaccharide (LPS)-induced responses in macrophage cell line J774.A1. Exposure of LPS-stimulated cells to (-)-linalool significantly inhibited nitrite accumulation in the culture medium without inhibiting the LPS-stimulated increase of inducible nitric oxide synthase (iNOS) expression, suggesting that the inhibitory activity of (-)-linalool is mainly due to the iNOS enzyme activity. In contrast, exposure of LPS-stimulated cells to (-)-linalool failed, if not at the highest concentration, both in inhibiting PGE(2) release and in inhibiting increase of inducible cyclooxygenase-2 (COX(2)) expression in the culture medium. Collectively, these results indicate that the reduction of NO production/release is responsible, at least partially, for the molecular mechanisms of (-)-linalool antinociceptive effect, probably through mechanisms where cholinergic and glutamatergic systems are involved.

GW274150, a novel and highly selective inhibitor of the inducible isoform of nitric oxide synthase (iNOS), shows analgesic effects in rat models of inflammatory and neuropathic pain

Nitric oxide (NO), synthesised by different isoforms of nitric oxide synthase (NOS), has been linked with the development and maintenance of nociception. We studied the role of the inducible isoform, iNOS, in two different rat pain models with an inflammatory component. iNOS was immunohistochemically detected locally in the paw 6h after Freund's Complete Adjuvant (FCA) injection, showing a plateau at 24-72 h and falling slowly in the following weeks. This correlated with the late phase of the hypersensitivity to pain revealed in the behavioural tests. A highly selective iNOS inhibitor GW274150 (1-30 mg/kg orally, 24h after FCA) suppressed the accumulation of nitrite in the inflamed paw indicating substantial iNOS inhibition. At the same time it partially reversed FCA-induced hypersensitivity to pain and edema in a dose-dependent manner. After Chronic Constriction Injury (CCI) surgery to the sciatic nerve, iNOS presence was only detected locally in the region of the nerve (inflammatory cells). GW274150 (3-30 mg/kg orally, 21 days after surgery) also reversed significantly the CCI-associated hypersensitivity to pain. No iNOS was detectable in dorsal root ganglia, spinal cord or brain in either model. This study demonstrates a role for peripherally-expressed iNOS in pain conditions with an inflammatory component and the potential value of iNOS inhibitors in such conditions.

Inhibition of p38 mitogen-activated protein kinase attenuates interleukin-1beta-induced thermal hyperalgesia and inducible nitric oxide synthase expression in the spinal cord

We have reported recently that intrathecal (i.t.) injection of interleukin-1beta (IL-1beta), at a dose of 100 ng, induces inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in the spinal cord and results in thermal hyperalgesia in rats. This study further examines the role of mitogen-activated protein kinase (MAPK) in i.t. IL-1beta-mediated iNOS-NO cascade in spinal nociceptive signal transduction. All rats were implanted with an i.t. catheter either with or without an additional microdialysis probe. Paw withdrawal latency to radiant heat is used to assess thermal hyperalgesia. The iNOS and MAPK protein expression in the spinal cord dorsal horn were examined by western blot. The [NO] in CSF dialysates were also measured. Intrathecal IL-1beta leads to a time-dependent up-regulation of phosphorylated p38 (p-p38) MAPK protein expression in the spinal cord 30-240 min following IL-1beta injection (i.t.). However, neither the phosphorylated extracellular signal-regulated kinase (p-ERK) nor phosphorylated c-Jun NH2-terminal kinase (p-JNK) was affected. The total amount of p38, ERK, and JNK MAPK proteins were not affected following IL-1beta injection. Intrathecal administration of either selective p38 MAPK, or JNK, or ERK inhibitor alone did not affect the thermal nociceptive threshold or iNOS protein expression in the spinal cord. However, pretreatment with a p38 MAPK inhibitor significantly reduced the IL-1beta-induced p-p38 MAPK expression by 38-49%, and nearly completely blocked the subsequent iNOS expression (reduction by 86.6%), NO production, and thermal hyperalgesia. In contrast, both ERK and JNK inhibitor pretreatments only partially (approximately 50%) inhibited the IL-1beta-induced iNOS expression in the spinal cord. Our results suggest that p38 MAPK plays a pivotal role in i.t. IL-1beta-induced spinal sensitization and nociceptive signal transduction.

Role of the immune system in chronic pain

During the past two decades, an important focus of pain research has been the study of chronic pain mechanisms, particularly the processes that lead to the abnormal sensitivity - spontaneous pain and hyperalgesia - that is associated with these states. For some time it has been recognized that inflammatory mediators released from immune cells can contribute to these persistent pain states. However, it has only recently become clear that immune cell products might have a crucial role not just in inflammatory pain, but also in neuropathic pain caused by damage to peripheral nerves or to the CNS.

Intrathecal interleukin-1β administration induces thermal hyperalgesia by activating inducible nitric oxide synthase expression in the rat spinal cord

The effect of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) on the inducible nitric oxide synthase-nitric oxide (iNOS-NO) cascade in nociceptive signal transduction was examined in the intact rat spinal cord. All rats were implanted with an intrathecal (i.t.) catheter; some were also implanted with an i.t. microdialysis probe. The paw withdrawal latency to radiant heat was used to assess thermal hyperalgesia. The iNOS protein expression in the spinal cord dorsal horn was examined by western blot analysis and NOS activity assay. NO production in the CSF dialysate was also measured. IL-1beta i.t. (100 ng) produced thermal hyperalgesia from 4 to 24 h after i.t. injection. The iNOS protein expression was induced at 4 h after i.t. IL-1beta injection, peaked at the 6th hour, and disappeared at 24 h. The iNOS activity showed a similar time-dependent change as the iNOS protein expression. NO release increased by 1.1- to 1.9-fold between 4 and 12 h, also with a peak at the 6th hour, after i.t. IL-1beta administration. Pretreatment with the iNOS inhibitor 1400W (10 microg, i.t.) 1 h before i.t. IL-1beta injection prevented all the responses of IL-1beta. Neither 1400W nor artificial CSF (aCSF) affected the thermal nociceptive threshold and NO production. These results demonstrate that i.t. administration of IL-1beta induced thermal hyperalgesia by activating the iNOS-NO cascade in the rat spinal cord. On the basis of the present findings, we suggest that i.t. administration of iNOS inhibitors may have potential in the treatment of inflammatory and neuropathic pain syndromes.

Principles of the bark of Amphipterygium adstringens (Julianaceae) with anti-inflammatory activity

Despite the fact that Amphipterygium adstringens (usually known as "cuachalalate") is used intensively in traditional medicine throughout México, there are, to our knowledge, no previous studies concerning the actual therapeutic, anti-inflammatory properties of this species. This lack of data prompted us to evaluate the aqueous (AE) and hexane (HE) extracts from A. adstringens in two models of acute inflammation: 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ear edema and carrageenan-induced paw edema. The results showed that HE possesses dose-dependent activity, while AE showed no anti-inflammatory effect on TPA-induced edema. Reverse effects were found in the carrageenan test, wherein AE showed a 73.5% of inhibition of edema, while HE showed only a 14.4% activity at 100 mg/kg body weight. These results could indicate that AE and HE possess different anti-inflammatory mechanisms of action. On the other hand, it is known that masticadienonic (1) and 3alpha-hydroxymasticadienonic (2) acids are the main constituents of the organic extract of A. adstringens bark. Because of this knowledge, we tested 1 and 2 in the same experimental models. The results showed that 2 possesses a dose-dependent effect, while 1 does not show a dose-dependent response in TPA-induced edema. In carrageenan-induced edema tests, both 1 and 2 showed almost the same activity (approximately 44% inhibition at 100 mg/kg body weight). In order to determine whether the anti-inflammatory activities of AE, HE, 1 and 2 are involved in the alteration of inducible nitric oxide synthase (iNOS) activity, we evaluated these substances by examining nitric oxide generation in lipopolysaccharide (LPS)-activated peritoneal macrophages. The results showed that 1 presented the highest activity (93.3%), followed by 2 (86.5%), while AE (57%) and HE (33.6%) showed the lowest. In the cytotoxic MTT assay, however only 1 and 2 showed any activity whatsoever.

Carrageenan-induced mouse paw oedema is biphasic, age-weight dependent and displays differential nitric oxide cyclooxygenase-2 expression

Injection of carrageenan 1% (50 microl) in the mouse paw causes a biphasic response: an early inflammatory response that lasts 6 h and a second late response that peaks at 72 h, declining at 96 h. Only mice 7- or 8-week old, weighing 32-34 g, displayed a consistent response in both phases. In 8-week-old mice, myeloperoxidase (MPO) levels are significantly elevated in the early phase at 6 h and reach their maximum at 24 h to decline to basal value at 48 h. Nitrate+nitrite (NO(x)) levels in the paw are maximal after 2 h and slowly decline thereafter in contrast to prostaglandin E(2) levels that peak in the second phase at the 72 h point. Western blot analysis showed that inducible nitric oxide synthase (iNOS) is detectable at 6 h and cyclooxygenase 2 (COX-2) at 24 h point, respectively. Analysis of endothelial nitric oxide synthase (eNOS), iNOS and COX-2 expression at 6 and 24 h in 3-8-week-old mice demonstrated that both eNOS and iNOS expressions are dependent upon the age-weight of mice, as opposite to COX-2 that is present only in the second phase of the oedema and is not linked to mouse age-weight. Subplantar injection of carrageenan to C57BL/6J causes a biphasic oedema that is significantly reduced by about 20% when compared to CD1 mice. Interestingly, in these mice, iNOS expression is absent up to 6 h, as opposite to CD1, and becomes detectable at the 24 h point. Cyclooxygenase (COX-1) expression is upregulated between 4 and 24 h after carrageenan injection, whereas in CD1 mice COX-1 remains unchanged after irritant agent injection. MPO levels are maximal at the 24 h point and they are significantly lower, at 6 h point, than MPO levels detected in CD1 mice. In conclusion, mouse paw oedema is biphasic and age-weight dependent. The present results are the first report on the differential expressions of eNOS, iNOS, COX-1 and COX-2 in response to carrageenan injection in the two phases of the mouse paw oedema.

Blunted stress responses in delayed type hypersensitivity in mice lacking the neuronal isoform of nitric oxide synthase

Nitric oxide (NO) is implicated in inflammation and hypothalamic-pituitary responses to immune stimuli; however, the specific role of NO from neurons during stress-induced immune responses remains unspecified. We measured antigen-specific delayed-type-hypersensitivity (DTH) responses in the skin of wild-type (WT) and neuronal nitric oxide synthase knockout (nNOS(-/-)) mice at baseline and after 2 h of restraint. Baseline corticosterone concentrations were higher in nNOS(-/-) than WT mice. However, stress-induced increases in corticosterone were dampened in nNOS(-/-) mice, and restraint suppressed DTH only in WT animals. Furthermore, WT mice lost more body mass after stress, and exhibited more anxiety-like behavior in the open field, than nNOS(-/-) mice. Neuronal NO appears to be involved in the neuroendocrine-immune response to stress, perhaps via glucocorticoid regulation.

The pharmacology of nitric oxide in the peripheral nervous system of blood vessels

Unanticipated, novel hypothesis on nitric oxide (NO) radical, an inorganic, labile, gaseous molecule, as a neurotransmitter first appeared in late 1989 and into the early 1990s, and solid evidences supporting this idea have been accumulated during the last decade of the 20th century. The discovery of nitrergic innervation of vascular smooth muscle has led to a new understanding of the neurogenic control of vascular function. Physiological roles of the nitrergic nerve in vascular smooth muscle include the dominant vasodilator control of cerebral and ocular arteries, the reciprocal regulation with the adrenergic vasoconstrictor nerve in other arteries and veins, and in the initiation and maintenance of penile erection in association with smooth muscle relaxation of the corpus cavernosum. The discovery of autonomic efferent nerves in which NO plays key roles as a neurotransmitter in blood vessels, the physiological roles of this nerve in the control of smooth muscle tone of the artery, vein, and corpus cavernosum, and pharmacological and pathological implications of neurogenic NO have been reviewed. This nerve is a postganglionic parasympathetic nerve. Mechanical responses to stimulation of the nerve, mainly mediated by NO, clearly differ from those to cholinergic nerve stimulation. The naming "nitrergic or nitroxidergic" is therefore proposed to avoid confusion of the term "cholinergic nerve", from which acetylcholine is released as a major neurotransmitter. By establishing functional roles of nitrergic, cholinergic, adrenergic, and other autonomic efferent nerves in the regulation of vascular tone and the interactions of these nerves in vivo, especially in humans, progress in the understanding of cardiovascular dysfunctions and the development of pharmacotherapeutic strategies would be expected in the future.

Therapeutic effect of the endogenous fatty acid amide, palmitoylethanolamide, in rat acute inflammation: inhibition of nitric oxide and cyclo-oxygenase systems

1. The anti-inflammatory activity of the endogenous fatty acid amide palmitoylethanolamide and its relationship to cyclo-oxygenase (COX) activity, nitric oxide (NO) and oxygen free radical production were investigated in the rat model of carrageenan-induced acute paw inflammation and compared with the nonsteroidal anti-inflammatory drug (NSAID) indomethacin. 2. Palmitoylethanolamide (1, 3, 5, 10 mg kg(-1); p.o.) and indomethacin (5 mg kg(-1); p.o.) were administered daily after the onset of inflammation for three days and the paw oedema was measured daily; 24 h after the last dose (fourth day) the rats were killed and the COX activity and the content of nitrite/nitrate (NO(2)(-)/NO(3)(-)), malondialdehyde (MDA), endothelial and inducible nitric oxide synthase (eNOS and iNOS) were evaluated in the paw tissues. 3. Palmitoylethanolamide had a curative effect on inflammation, inhibiting the carrageenan-induced oedema in a dose- and time-dependent manner. This effect was not reversed by the selective CB(2) receptor antagonist (N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3 carboxamide) (SR144528), 3 mg kg(-1) p.o. On the fourth day after carrageenan injection, COX activity and the level of NO(2)(-)/NO(3)(-), eNOS and MDA were increased in the inflamed paw, but iNOS was not present. Palmitoylethanolamide (10 mg kg(-1)) and indomethacin markedly reduced these increases. 4. Our findings show, for the first time, that palmitoylethanolamide has a curative effect in a model of acute inflammation. The inhibition of COX activity and of NO and free radical production at the site of inflammation might account for this activity.

Therapeutic modulation of inflammatory gene transcription by kinase inhibitors

Altered gene expression contributes to the aetiology of inflammatory disease by modulation of the concentration of disease-related proteins. The expression of inflammatory genes is controlled through the concerted actions of specific transcription factors. Signal transduction networks positively or negatively regulate the activity of these transcription factors. Key components of these networks are protein kinases, which phosphorylate substrates on tyrosine, threonine or serine residues. During the disease process, pro-inflammatory signalling at the cell surface leads to a cascade of kinase activation, which ultimately culminates in modulation of the activity of transcription factors. Thus, pharmacological inhibition of protein kinases is a potential therapeutic strategy to treat inflammation. There are approximately 500 protein kinases in the human genome. Targeted small molecule inhibitors of these kinases should allow for tissue- and disease-specific therapies of unprecedented selectivity. Heralding this new era in molecular medicine is imatinib (Gleevec, Norvartis) a recently marketed tyrosine kinase inhibitor. This review focuses on kinase inhibitors that are currently in development for inflammatory diseases and the transcription factors that are involved.

Protein nitration in cutaneous inflammation in the rat: essential role of inducible nitric oxide synthase and polymorphonuclear leukocytes

1: We have examined the relationship between neutrophil accumulation, NO(*) production and nitrated protein levels in zymosan-mediated inflammation in rat skin in vivo. 2: Rats were anaesthetized and cutaneous inflammation was induced by zymosan (injected intradermally, i.d.). Experiments were carried out up to 48 h, in recovery procedures as appropriate. Assays for neutrophil accumulation (measurement of myeloperoxidase), nitric oxide (assessment of NO(2)(-)/NO(3)(-)) and nitrated proteins (detected by ELISA and Western blot) were performed in skin extracts. 3: The results demonstrate a close temporal relationship between these parameters. Samples were assayed at 1, 4, 8, 24 and 48 h after i.d. injection of zymosan. The highest levels measured of each parameter (P<0.001 compared with vehicle) were found at 4-8 h, with a reduction towards basal levels by 24 h. 4: Selective depletion of circulating neutrophils with anti-neutrophil antibody abolished neutrophil accumulation and protein nitration. In addition substantially decreased NO levels were found. 5: A selective inducible nitric oxide synthase (iNOS) inhibitor, N-3-aminomethyl-benzyl-acetamidine-dihydrochloride (1400W) also significantly reduced neutrophil levels and NO production and substantially inhibited protein nitration. 6: We conclude that the neutrophil leukocyte plays an essential role in the formation of iNOS-derived NO and nitrated proteins in inflammation, in a time-dependent and reversible manner. The NO-derived iNOS also has a role in stimulating further neutrophil accumulation into skin. This suggests a close mechanistic coupling between neutrophils, NO production and protein nitration.